a. Field of the Invention
The present invention relates to a method of manufacturing reinforced resin moldings.
B. Description of the Prior Art
The reinforced resins hitherto known have been obtained by, for instance, a method wherein glass fiber is previously impregnated with a thermosetting monomer and thereafter polymerizing it in the mold, or a method wherein a thermosetting prepolymer is applied as the adhesive sequentially after setting glass fiber in the mold beforehand and further heating and curing it so as to harden it. The adhesive prevalently employed for these conventional methods is the polyester-type thermosetting resin.
Meanwhile, there have been known instances of applying thermoplastic resins such as polyethylene, polypropylene and polystyrene-polyvinyl chloride as the adhesive to the reinforced resin. However, in the case of the reinforced resins obtained by these conventional methods, the adhesive between the fiber and the resin is not always firm, and therefore, improvement of such properties as bending strength, impact strength, water-durability and thermal stability has been hoped for. Particularly the lack of firmness of the adhesion between the fiber and the resin entails the drawbacks that the strength in water is remarkably reduced as it invites the permeation of water into the bonded surface of the fiber and the resin. This remarkable reduction of the strength in water tends to occur also in the reinforced resins obtained by the conventional kneading method as well as the polymerization method as discussed in the following.
In the case of kneading upon adding the fiber to a thermoplastic resin, due to the cutting of the fiber and the generation of friction heat of the polymer, the properties of the resulting reinforced resin are apt to be rather inferior. There is also known the method of employing the substance obtained by depositing vinyl-type solid polymer onto the surface of the fiber by applying the known polymerization initiator as the molding material for reinforced resin, but in the thus obtained thermoplastic resin.about.fiber complex, the degree of coating the fiber with thermoplastic resin is so low that the bonding strength between the fiber and the resin is weak and the strength of the resulting product tends to be insufficient.
Further, as another prevalent method of obtaining a molding material by coating fiber with resin, there is a method of coating the fiber which comprises dispersing the fiber and monomer in a polar solvent (hydrophilic solvent) such as water and methanol, adding a radical polymerization initiator such as organic peroxide, hydrogen peroxide, persulfate and azobisisobutyronitrile to the resulting dispersion to effect polymerization and depositing the thus produced polymer onto said fiber. However, according to this method, because of the presence of said polymerization initiator in said monomer and medium, polymerization would take place in places other than the surface of the solid particles, so that the probability of said polymer coating the fiber is rather low.
The present inventors have carried on a series of studies with a view to developing a method of remarkably improving the strength of the moldings of reinforced resin consisting of the aforesaid thermoplastic resin and fiber, and have come to accomplish the present invention.